AN IR SPECTROSCOPIC SEARCH FOR THE 51 PEG PLANET

We have observed 51 Peg with UKIRT and IRTF, seeking to detect
absorption lines from the material evaporated from its Jupiter-mass
companion by the stellar wind from 51 Peg. Observations were taken
on Aug. 18, 19, 27, 29, Sep. 3 and 4, 1996 - nights when the planet
was either at quadratures or at transit.

As the companion's orbital plane is thought to be near the
line-of-sight, there is some chance that an extended atmosphere would
occult the star. This in turn may be detected by comparing the
infrared spectrum of the star at on-transit and off-transit times.

Hydrodynamic equations have been solved in the collisional inner part
of the corona, whereas the Jeans formulation is used in the
exosphere. Enhanced EUV flux conditions have been considered. It has
been shown that a large EUV flux may yield the formation of an
extended collisional corona of size typically 10 planetary radii.

Due to the bombardment of the fluid corona by stellar wind protons,
very high temperatures are expected to prevail in the outer regions
of the corona (up to 1 million degrees), and high values of the
hydrogen escape flux may be reached (although it is not guaranteed
that photochemistry can supply the flow at the required level).

The reduction of the observations is currently under way and this
poster given preliminary results.